全文获取类型
收费全文 | 7888篇 |
免费 | 445篇 |
出版年
2023年 | 58篇 |
2020年 | 153篇 |
2019年 | 199篇 |
2018年 | 309篇 |
2017年 | 286篇 |
2016年 | 345篇 |
2015年 | 225篇 |
2014年 | 214篇 |
2013年 | 2091篇 |
2012年 | 247篇 |
2011年 | 271篇 |
2010年 | 255篇 |
2009年 | 238篇 |
2008年 | 207篇 |
2007年 | 207篇 |
2006年 | 174篇 |
2005年 | 112篇 |
2004年 | 103篇 |
2003年 | 99篇 |
2002年 | 115篇 |
2001年 | 147篇 |
2000年 | 108篇 |
1999年 | 115篇 |
1998年 | 92篇 |
1997年 | 83篇 |
1996年 | 86篇 |
1995年 | 70篇 |
1994年 | 59篇 |
1993年 | 72篇 |
1992年 | 71篇 |
1991年 | 60篇 |
1990年 | 60篇 |
1989年 | 57篇 |
1988年 | 52篇 |
1987年 | 60篇 |
1986年 | 61篇 |
1985年 | 70篇 |
1984年 | 79篇 |
1983年 | 84篇 |
1982年 | 69篇 |
1981年 | 67篇 |
1980年 | 66篇 |
1979年 | 61篇 |
1978年 | 66篇 |
1977年 | 67篇 |
1976年 | 61篇 |
1975年 | 71篇 |
1974年 | 42篇 |
1973年 | 38篇 |
1972年 | 41篇 |
排序方式: 共有8333条查询结果,搜索用时 78 毫秒
981.
982.
Tomas M. Koontz 《政策研究杂志》2005,33(3):459-481
There is a growing movement toward collaborative stakeholder participation in environmental policy. Rather than calling for a reliance on government officials to solve environmental problems, this approach calls for empowering a community of stakeholders to contribute meaningfully. Scholars examining citizen participation have investigated the performance of such efforts. This study examines one important aspect of performance, the impact of stakeholder participation on policymaking at the local level. A multiple‐case analysis of county‐level, community‐based task forces working on farmland preservation planning in Ohio, U.S., reveals patterns of policymaking processes and the near‐term impacts of collaborative planning. These patterns are linked to scholarship using prior empirical studies as well as the Institutional Analysis and Development framework, which integrates physical, social, and institutional variables to examine collective decision‐making related to natural resources. Results indicate that the degree of policy change is associated closely with local contextual factors, rather than internal group factors often emphasized in studies of citizen advisory committees and collaborative groups. 相似文献
983.
E. Gliozzo D. D’Aco I. Memmi Turbanti A. Galli M. Martini E. Sibilia 《Archaeological and Anthropological Sciences》2009,1(2):77-85
Twenty-one samples of likely Roman, likely Islamic and unknown common ware from the archaeological site of Thamusida (Rabat, Morocco) were analysed in order to anchor selected types of pottery to a limited time span and, possibly, to a production
area and technology. Analytical techniques were thermoluminescence, optical microscopy, scanning electron microscopy and X-ray
fluorescence. The results arising from this research are definitely useful for the study of the site of Thamusida as well as for all researchers involved in archaeological and archaeometrical research in Morocco. Chronologies proposed
on a typological base have been denied twice: a likely Islamic cup dates back to the second century a.d.; vice versa, a stewpot, framed into the Roman period, resulted to be an eighth century a.d. production. Moreover, the identification of an eighteenth century ceramic production is of outstanding importance, as it
characterises a completely unknown production. Regarding the production area, four samples of both Roman and Islamic periods
have been recognised as local productions of Thamusida. 相似文献
984.
985.
U‐series dating was used to determine the growth rate of a feldspar‐to‐clay weathering rind in a mid‐Holocene Cascade–Olcott tradition andesite core, and luminescence dating (last exposure to sunlight) was used to date fine‐grained feldspars scraped from the surfaces of similar buried artefacts from a 14C‐sediment‐dated archaeological site (45KI464) on the wet western slope of the Cascade Mountains of Washington. For U‐series dating, we measured 226Ra excess (226Ra excess =226Ra –230Th) in five stratigraphic depth controlled rind scrapings. 238U, 232Th and 230Th were counted by alpha spectrometry, and 226Ra and 210Pb were counted by gamma spectrometry on each sub‐sample. 相似文献
986.
Previously published data on the chemical compositions and microstructures of copper‐ and cobalt‐blue frit, glass and faience from the New Kingdom site of Amarna in Egypt ( Shortland 2000 ) are summarized. The data are then used to infer the raw materials and processes employed in the production of these vitreous materials. The results suggest that crushed quartz pebbles were the source of the quartz for all the materials, but that different sources of alkali, both natron and a range of plant ashes, were used in the production of each material. It seems probable that the cobalt‐rich alum colorant was pre‐treated before use by precipitating cobalt hydroxide from a solution of the alum by the addition of natron. It is further hypothesized that cobalt‐blue glass was produced by melting the cobalt‐blue frit together with additional plant ash and possibly quartz. Finally, it is suggested that, in glazing the cobalt‐blue Variant D faience first produced in the 18th Dynasty, the efflorescence or application method was selected according to object type. 相似文献
987.
Samples of Roman thin‐walled ware from Segesta (northwestern Sicily), dating back to the early Imperial period, were studied by optical microscopy (OM) and Neutron Activation Analysis (NAA). Up to now, this class of Roman fine tableware has only occasionally been evaluated archaeometrically. Nevertheless, numerous production centres are believed to have been simultaneously active in the western Mediterranean area. Petrographic and chemical data seem to be in agreement with the archaeological hypothesis of local manufacture in Segesta for most of the analysed samples, through a comparison with kiln wasters and local raw materials. The effectiveness of thin‐section petrography for determining the provenance of such a tiny tempered class of pottery and the integrated use of two different grouping procedures (petrography and chemistry) were also tested. 相似文献
988.
Lead isotope analyses have been undertaken on a group of Islamic lead‐glazed pottery artefacts from Fustat, Egypt, spanning the period from the eighth to the 14th century ad , that had previously been the subject of a comprehensive typological, chronological, petrographic and technological study. Comparison of the lead isotope ratios for the glazes with those for lead ores from Egypt, Iran, Tunisia, Anatolia, Greece, Sardinia and Spain provided information on the possible sources of the lead used in the production of the glazes. The results show that the lead used in glaze production by the Islamic potters at Fustat was most probably obtained from distant ore sources in Iran or Tunisia, Sardinia, Spain and the Taurus Mountains. Different ore sources were favoured in different periods and, to a limited extent, for different types of pottery, but at no time did the Fustat potters use the potentially more accessible Egyptian ore sources. 相似文献
989.
Peter M. Atkinson Sally E. German David A. Sear Michael J. Clark 《Geographical analysis》2003,35(1):58-82
The relations between riverbank erosion and geomorphological variables that are thought to control or influence erosion are commonly modelled using regression. For a given river, a single regression model might befitted to data on erosion and its geomorphological controls obtained along the river's length. However, it is likely that the influence of some variables may vary with geographical location (i.e., distance upstream). For this reason, the spatially stationary regression model should be replaced with a non‐stationary equivalent. Geographically weighted regression (GWR) is a suitable choice. In this paper, GWR is extended to predict the binary presence or absence of erosion via the logistic model. This extended model was applied to data obtained from historical archives and a spatially intensive field survey of a length of 42 km of the Afon Dyfi in West Wales. The model parameters and the residual deviance of the model varied greatly with distance upstream. The practical implication of the result is that different management practices should be implemented at different locations along the river. Thus, the approach presented allowed inference of spatially varying management practice as a consequence of spatially varying geomorphological process. 相似文献
990.